Traditional wearable devices activate quickly upon detection of any trigger, such as an event-like movement or voice command. In general, various sensors are populated in wearable devices, which can detect activity such as movement or a change in environment such as an ambient light, background noise or voice command. Many sensors have to be polled repetitively (e.g., every 50 ms) by a sensor hub in order to detect a trigger event. During the polling period, the sensor hub may check each sensor for activity detection. Once polling is done, if there was no activity detected on the sensors, the sensor hub returns back to sleep (e.g., retention state). The state of the sensor hub, however, can quickly change to an active state upon a trigger event. The processing of the signal from an active sensor is performed by a main central processor unit (MCU).